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What are the types of flames that may be produced in gas welding?

Answer: Types of Flames

In oxy‐acetylene gas welding, flame is the most important means to control the welding joint and the welding process.

There are three basic types of oxy‐acetylene flames:

1. Neutral flame (Acetylene and oxygen in equal proportions).

(a) Inner cone indicates incomplete combustion.

(b) Outer bluish color indicates complete combustion.

(c) Maximum temperature of flame is induced at the intersection of inner cone and outer cone.

(d) During combustion of acetylene large quantity of water is produced, to evaporate this water, large amount of heat is carried away.

Uses :

(a) It is used for ferrous and non‐ferrous metals strictly prohibited for zinc alloys. For example, brass because zinc is present in brass, it will get evaporated.
(b) It can be used for high melting point materials.

2. Carburizing flame or reducing flame (excess of acetylene) :

(a) Excess supply of acetylene.

(b) Due to less supply of oxygen, combustion is incomplete.

(c) Temperature generated in flame is less.

Uses :

(a) Because of lower average temperature, high melting point metals cannot be joined.

(b) Because of un‐burnt carbon present in flame, this carbon may absorb by the iron during joining of ferrous metals and increase brittleness and reduce toughness. So it should not be used for joining of ferrous materials.

(c) This is mostly used for high carbon steels.

3. Oxidizing flame (excess of oxygen) :

(a) Here excess amount of oxygen is present.

(b) Due to presence of excess amount of oxygen complete combustion of acetylene is taking place.

(c) The temperature of flame is maximum than any other flames.

Uses :

(a) Because of higher average temperature, it can be used for high melting point materials.

(b) Oxidizing flame is used to weld metal like copper (Cu). It is not suitable for highly reactive metals like, Al, Mn etc., because of excess supply of oxygen there is a possibility of oxidation.

(c) It can be used for joining brass workpiece.

Types of Flames Types of Flames